U.S. patent application number 12/617381 was filed with the patent office on 2010-05-13 for high noble dental alloy.
Invention is credited to Paul J. Cascone, Arun Prasad.
Application Number | 20100119400 12/617381 |
Document ID | / |
Family ID | 42165367 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100119400 |
Kind Code |
A1 |
Prasad; Arun ; et
al. |
May 13, 2010 |
HIGH NOBLE DENTAL ALLOY
Abstract
A silver free high noble dental alloy comprising at least 60 wt.
% noble materials, where 40 wt. % of the material is gold; at least
2.5 wt. % gallium, at least about from 2 to 4 wt. % cobalt; and at
least from about 0.01 to 0.25 wt. % lithium and/or boron; and a
principal balance of palladium is provided. Dental products and
methods of manufacturing dental products using such a high noble
dental alloys are also provided.
Inventors: |
Prasad; Arun; (Cheshire,
CT) ; Cascone; Paul J.; (Del Mar, CA) |
Correspondence
Address: |
KAUTH , POMEROY , PECK & BAILEY ,LLP
2875 MICHELLE DRIVE, SUITE 110
IRVINE
CA
92606
US
|
Family ID: |
42165367 |
Appl. No.: |
12/617381 |
Filed: |
November 12, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61113917 |
Nov 12, 2008 |
|
|
|
Current U.S.
Class: |
419/1 ; 420/463;
420/580; 75/352 |
Current CPC
Class: |
C22C 5/02 20130101; C22C
30/00 20130101; B22F 2998/10 20130101; Y02P 10/25 20151101; A61K
6/844 20200101; B22F 2998/10 20130101; B22F 9/08 20130101; B22F
10/20 20210101; B22F 2998/10 20130101; B22F 9/08 20130101; B22F
10/20 20210101 |
Class at
Publication: |
419/1 ; 420/463;
420/580; 75/352 |
International
Class: |
B22F 3/105 20060101
B22F003/105; C22C 5/04 20060101 C22C005/04; C22C 30/00 20060101
C22C030/00; B22F 9/00 20060101 B22F009/00 |
Claims
1. A high noble dental alloy comprising:
Pd.sub.1-a(AU.sub.bCO.sub.cX.sub.d(GaY).sub.eZ.sub.f).sub.a where X
is at least one material selected from the group consisting of
lithium and boron; where Y is at least one material selected from
the group consisting of germanium, tin, indium, zinc and manganese;
where Z is at least one material selected from the group consisting
of ruthenium, rhenium and iridium; where a is the sum of b, c, d, e
and f; and where b is from 40 to 44 wt. %, c is from about 2 to 4
wt. %, d is from about 0.01 to 0.25 wt. %, e is from about 2.5 to 6
wt. % where gallium must comprise at least 2.5 wt. % of the total
alloy composition, and f is from about 0 to 1 wt. %.
2. The high noble dental alloy of claim 1, where b is 40 wt. %.
3. The high noble dental alloy of claim 1, where c is about 3 wt.
%.
4. The high noble dental alloy of claim 1, where d is about 0.1 wt.
%.
5. The high noble dental alloy of claim 4, where X is lithium.
6. The high noble dental alloy of claim 1, where e is about 6
wt.
7. The high noble dental alloy of claim 6, where Y is a mixture of
gallium and tin.
8. The high noble dental alloy of claim 7, where gallium comprises
3 wt. % of the alloy.
9. The high noble dental alloy of claim 1, where f is about 0.2 wt.
%.
10. The high noble dental alloy of claim 9, where Z is a mixture of
ruthenium and rhenium.
11. The high noble dental alloy of claim 10, where ruthenium and
rhenium each comprise 0.1 wt. % of the alloy.
12. The high noble dental alloy of claim 1, wherein the alloy
further comprises less than 5 wt. % of at least one trace additive
selected from the group consisting of copper, nickel and iron.
13. The high noble dental alloy of claim 1, wherein the alloy
comprises 50.7 wt. % palladium, 40 wt. % gold, 3 wt. % cobalt, 3
wt. % gallium, 3 wt. % tin, 0.1 wt. % lithium, 0.1 wt. % rhenium
and 0.1 wt. % ruthenium.
14. A dental product comprising: a substrate for dental
application, said substrate being formed of a high noble dental
alloy comprising:
Pd.sub.1-a(AU.sub.bCO.sub.cX.sub.d(GaY).sub.eZ.sub.f).sub.a where X
is at least one material selected from the group consisting of
lithium and boron; where Y is at least one material selected from
the group consisting of germanium, tin, indium, zinc and manganese;
where Z is at least one material selected from the group consisting
of ruthenium, rhenium and iridium; where a is the sum of b, c, d, e
and f; and where b is from 40 to 44 wt. %, c is from about 2 wt. %
to 4 wt. %, d is from about 0.01 to 0.25 wt. %, e is from about 2.5
to 6 wt. % where gallium must comprise at least 2.5 wt. % of the
total alloy composition, and f is from about 0 to 1 wt. %.
15. The dental product of claim 14, where b is 40 wt. %.
16. The dental product of claim 14, where c is about 3 wt. %.
17. The dental product of claim 14, where d is about 0.1 wt. %.
18. The dental product of claim 17, where X is lithium.
19. The dental product of claim 14, where e is about 6 wt.
20. The dental product of claim 19, where Y is a mixture of gallium
and tin.
21. The dental product of claim 20, where gallium comprises 3 wt. %
of the alloy.
22. The dental product of claim 14, where f is about 0.2 wt. %.
23. The dental product of claim 22, where Z is a mixture of
ruthenium and rhenium.
24. The dental product of claim 23, where ruthenium and rhenium
each comprise 0.1 wt. % of the alloy.
25. The dental product of claim 14, wherein the alloy further
comprises less than 5 wt. % of at least one trace additive selected
from the group consisting of copper, nickel and iron.
26. The dental product of claim 14, wherein the alloy composition
comprises 50.7 wt. % palladium, 40 wt. % gold, 3 wt. % cobalt, 3
wt. % gallium, 3 wt. % tin, 0.1 wt. % lithium, 0.1 wt. % rhenium
and 0.1 wt. % ruthenium.
27. A method of forming a dental product comprising the steps of:
providing a high noble dental alloy comprising:
Pd.sub.1-a(AU.sub.bCO.sub.cX.sub.d(GaY).sub.eZ.sub.f).sub.a where X
is at least one material selected from the group consisting of
lithium and boron, where Y is at least one material selected from
the group consisting of germanium, tin, indium, zinc and manganese,
where Z is at least one material selected from the group consisting
of ruthenium, rhenium and iridium, where a is the sum of b, c, d, e
and f, and where b is from 40 to 44 wt. %, c is from about 2 wt. %
to 4 wt. %, d is from about 0.01 to 0.25 wt. %, e is from about 2.5
to 6 wt. % where gallium must comprise at least 2.5 wt. % of the
total alloy composition, and f is from about 0 to 1 wt. %; and
shaping the dental alloy to form a dental product.
28. The method of claim 27, wherein the step of shaping comprises
converting the alloy into a powder.
29. The method of claim 28, wherein the step of shaping is selected
from the group consisting of casting, molding, milling and laser
sintering.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional. Patent
Application No. 61/113,917, filed Nov. 12, 2008, the disclosure of
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention concerns a silver free, high noble dental
alloy (as defined by American Dental. Association's classification
of alloys, i.e., alloys containing at least 60 wt. % noble metal
content where at least 40 wt. % of the noble metal content is gold)
for use with porcelains-fused to-metal and crown and bridge casting
techniques
BACKGROUND OF THE INVENTION
[0003] Dental alloys employed in the porcelain-fused-to-metal
processing technique may be classified into several groups,
including noble alloys and high noble alloys. The cost of the alloy
is dependent upon the commodity prices of the alloy components. For
example, as of November, 2008 the costs of the major components of
such alloys are: gold $734 per Troy ounce, palladium $ 199 per Troy
ounce; cobalt $1 per Troy ounce; and nickel $0.3 per Troy ounce.
The economic advantage of using as little of the high cost gold or
palladium metals is immediately obvious. In general, however,
silver is used as a replacement in alloys with reduced gold content
because its properties are very compatible with gold.
[0004] Unfortunately, the presence of silver can itself lead to
other problems, including the difficulty found in matching the
coefficient of thermal expansion (CTE) of silver to most
commercially available porcelains, and the strong tendency that
silver has to react with its surrounding, which can lead to an
unacceptable level of discoloration in the porcelain of the dental
device. As a result, significant effort has been exerted to find
high noble content alloys that are silver free while still being
compatible with conventional dental porcelains.
[0005] A detailed analysis of commercially available silver-free
alloys worldwide reveals that there are no silver free alloys with
the lowest level of Au needed for high noble (HN) classification
(i.e., noble metals (Au+Pt Groups).gtoreq.60 wt % with the proviso
that Au.gtoreq.40 wt %). It is to be noted that silver-free alloys
having Au concentrations either .gtoreq.45 wt. % or .ltoreq.35 wt.
% are available. (See, e.g., U.S. Pat. Nos. 4,123,262; 4,179,286;
4,539,176 and 4,591,483.) However, the latter alloys suffer from
being classified as lower category noble (N) alloys (i.e., alloys
having a noble metal content of 25 wt. %), and the former alloys
require the use of excessive amounts of Au, which render these
alloys costly to use. Thus, there is a need for a silver free HN
alloy with a concentration of Au that is as low as possible
(.about.40 wt. %).
BRIEF SUMMARY OF THE INVENTION
[0006] Thus, there is provided in the practice of this invention
according to a presently preferred embodiment, a workable HN dental
alloy comprising at least 60 wt. % noble metal, where from about 40
to 44 wt. % of the noble metal is gold, and where the principal
balance of the alloy, absent small contributions from additives, is
palladium. The alloy further comprises at least 2.5 wt. % gallium,
from about 2 to 4 wt. % cobalt and from about 0.01 to 0.25 wt. %
lithium and/or boron to extend the use of the alloy with porcelains
having wider coefficients of thermal expansions (GTE).
[0007] In another embodiment of the invention the alloy may include
about 6 wt. % of a combination of one or more of germanium,
gallium, tin, indium, zinc and manganese, where the amount of
gallium is .gtoreq.2.5 wt %.
[0008] In yet another embodiment of the invention the alloy may
include up to about 1 wt. % of one or more of ruthenium, rhenium
and iridium.
[0009] In still another embodiment of the invention the alloy
composition comprises 40 wt. % gold; 50.7 wt. % palladium; 3 wt. %
gallium; 3 wt. % tin; 3 wt. % cobalt; 0.1 wt. % ruthenium; 0.1 wt.
% rhenium; and 0.1 wt. % lithium.
[0010] In still yet another embodiment the invention is directed to
a dental product fabricated using the alloy described above.
[0011] In still yet another embodiment the invention is directed to
a method of manufacturing a dental product fabricated from the
alloy (or its powder) described above using a technique selected
from casting, molding, milling or laser sintering.
DETAILED DESCRIPTION OF THE INVENTION
[0012] A high noble dental alloy is considered to be one with at
least 60 wt. % noble metal content, the noble metals include
ruthenium, platinum, palladium, iridium, osmium, rhodium and gold,
where the content of gold must comprise at least 40 wt. % of the
alloy. The alloy provided herein is a high noble alloy for use with
high coefficient of thermal expansion (CTE) porcelains that
contains the minimum possible concentration of gold. The alloy
accomplishes this dual function by having more than 60 wt. %
palladium and gold, where the gold only constitutes from around 40
to 44 wt. % of the total, at least 2.5 wt. % gallium, from 2 to 4
wt. % cobalt and 0.01 to 0.25 wt. % (lithium and/or boron). It
should be noted that unless otherwise indicated all percentages
herein are by weight.
[0013] The choice of palladium has both metallurgical and economic
benefits. For example, consider the price of gold and the platinum
group metals as of November 2008:
TABLE-US-00001 Rhodium $1600 Platinum $838 Gold $734 Iridium $440
Ruthenium $235 Palladium $199
Palladium has a lower cost relative to the other platinum group
metals so there is an economic advantage to maximize the palladium
content in place of gold and the other platinum group elements.
[0014] From a metallurgical perspective, palladium acts as an alloy
strengthener, is a thermal expansion adjuster for the alloys (to
better match thermal expansion of dental porcelains) and reduces
the alloy's oxidation rate. The palladium also protects the alloy
from corrosion. The palladium serves to enoble the alloy to protect
the alloy from adverse reactions. The current application
identifies a HN alloy having high palladium content suitable for
dental applications that defies conventional formulations by
maintaining a percentage of gold at or above 40 wt. %, but no
higher than 44 wt. %.
[0015] The invention also incorporates the addition of from 2 to 4
wt. % cobalt to adjust the thermal expansion properties of the
alloys in order to make them compatible with high CTE porcelains,
and from 0.01 to 0.25 wt. % of one or both lithium and boron to
suppress the formation of cobalt oxides that would otherwise form
an unappealing dark line at the porcelain-metal junction. It was
also found that for an equivalent amount, lithium is more effective
than boron in this regard. Both cobalt and lithium also tend to
modify the grain structure of the alloy making it more machinable.
In addition, lithium is not only a deoxidizer but also a getter for
hydrogen. Finally, at least 2.5 wt. % of gallium is included to
lower the melting range, and improve the castability and mechanical
properties of the alloys
[0016] Accordingly, an family of alloys suitable for practice of
this invention would comprise at least 60 wt. % noble metal, where
40 to 44 wt. % is gold; from 2 to 4 wt. % cobalt; at least 2.5 wt.
% gallium, from 0.01 to 0.25 wt. % lithium and/or boron.
[0017] Although only the essential compositional materials are
described above, it should be understood that the alloy may also
contain other elements to improve the metallurgical properties of
the material, including up to 6 wt. % of a combination of
germanium, gallium, tin, indium, zinc and manganese. Specifically,
small concentrations (up to .about.6 wt. %) of these materials and
particularly gallium can serve to lower the melting range, and
improve the castability and mechanical properties of the alloys. In
a preferred embodiment, the range of these materials is from about
2.5 to 6 wt. %, but where at least about 2.5 wt % of these
materials must be gallium. However, excessive amount of Ga lowers
the solidus temperature to a range where distortion becomes an
issue when the alloy is used against medium fusing, conventional
porcelains. In addition, the alloy may contain up to about 1.0 wt.
% rhenium, ruthenium and iridium for grain refinement. Finer grains
eliminate hot tears during casting operations and the castings are
more readily ground to a smooth and shiny finish.
[0018] A summary of the compositional ranges of both the required
and optional materials is provided in Table 1, below.
TABLE-US-00002 TABLE 1 Compositional Ranges Percent Composition
Materials (wt. %) Au 40-44 Pd Balance Co 2-4 Li and/or B 0.01-0.25
1 or more of: Ge, Ga, Sn, In, Zn & 2.5-~6 Mn (where Ga is
.gtoreq.2.5) 1 or more of: Ru, Re, & Ir 0-1
[0019] Thus in a preferred embodiment, the alloy is a HN alloy with
a noble metal content of more than 60 wt. %, where gold makes up at
least 40 wt. % of the noble material; about 3 wt. % gallium; about
3 wt. % tin; about 3 wt. % cobalt; about 0.1 wt. % ruthenium; about
0.1 wt. % rhenium; and about 0.1 wt. % lithium. The amount of
palladium in this embodiment is preferably about 50.7 wt. %.
[0020] It is appreciated that the above compositions suitable for
use with dental appliances are not exclusive. Those of skill in the
art will be aware that some of the materials can be substituted or
additional materials may be added without altering the key
properties of the alloys of the current invention. For example, it
is well known that small amounts of palladium can be substituted
with copper, nickel and iron. Alternatively, small concentrations
(less than 5 wt. %) of these materials may also be added or be
found in the alloy as impurities without affecting the properties
of the overall composition. Ruthenium can also be substituted by
Iridium.
[0021] Although the above description has focused on a range of
compositions for the alloys of the current invention, the invention
is also directed to dental products made from the alloys, and to
methods of manufacturing dental products from the alloys. In
general, such methods will include the steps of providing an alloy
having a composition in accordance with the above description and
then shaping that alloy using any suitable means. In this regard,
the alloy of the instant invention allows for the use of a number
of conventional shaping techniques, such as, casting and molding.
Moreover, the alloys of the current invention also allow for the
use of more recent advances in shaping technologies, such as, for
example, CAD/CAM milling and selective laser sintering. It should
be understood that any of these techniques or a combination thereof
may be used with the alloy of the current invention.
[0022] Specifically, the alloy may be cast into blocks using
traditional dental laboratory techniques or may be atomized into
powders making it especially suited for use with newer CAD/CAM and
powder metallurgical applications where no casting is required. In
one such technique, substrates or final restorations can be milled
from blocks made from these alloys. As powders, these alloys can be
used either to create three dimensional preforms utilizing
appropriate binders and then be sintered, or can be directly
sintered/melted such as for example, with a laser, to create
substrates or final restoratives. Exemplary disclosures of such
processes can be found, for example, in U.S. Pat. Nos. 7,084,370
and 6,994,549, the disclosures of which are incorporated herein by
reference. It should be understood that while some prior art laser
sintering techniques specify a specific range of useable alloy
particulate sizes, the alloys of the current invention are
contemplated for use in laser sintering techniques over all
possible particulate size ranges.
[0023] Those skilled in the art will appreciate that the foregoing
examples and descriptions of various preferred embodiments of the
present invention are merely illustrative of the invention as a
whole, and that variations in the relative composition of the
various components of the present invention may be made within the
spirit and scope of the invention. For example, it will be clear to
one skilled in the art that typical impurities and/or additives may
be included in the compositions discussed above that would not
affect the improved properties of the alloys of the current
invention nor render the alloys unsuitable for their intended
purpose. Accordingly, the present invention is not limited to the
specific embodiments described herein but, rather, is defined by
the scope of the appended claims.
* * * * *